1. Field of the Invention
The invention relates generally to the field of interferometry. More particularly, the invention relates to an interferometric source of multi-color, multi-beam entangled photons.
2. Discussion of the Related Art
Quantum mechanical entanglement holds the promise of fundamental advances in sensing, metrology, computing, and communications. Polarization experiments at numerous laboratories [D. Bouwmeester et al., xe2x80x9cExperimental Quantum Teleportation,xe2x80x9d Nature 390, 575 (1997)] demonstrate the capability of generating entangled photons and entangled interferometry over long distances. Their results indicate violations of Bell""s inequalities, showing that the observed interference is quantum rather than classical. However, the nature of polarization entanglement does not easily lend itself to remote sensing, communications, or microscopy.
Rarity and Tapster, [Rarity and Tapster, xe2x80x9cExperimental violation of Bell""s inequality based on phase and momentum,xe2x80x9d Phys. Rev. Lett., 64:2495, 1990.] constructed a coincidence-based measurement system that showed two-color fourth-order interference. The Rarity and Tapster system used two separate beam splitters with four emergent beams. The Rarity and Tapster system reduced a degree of uncertainty (it erased momentum information) and produced a fourth-order (temporal) interference. What is needed is an approach that removes further degrees of uncertainty from multi-color photons. What is also needed is an approach that can produce an Nth-order interference (where N greater than 4) with fewer than four emergent beams.
A shortcoming of the Rarity and Tapster system is that interferometric measurement devices that utilize this system can not operate with consistent accuracy over a wide range of displacement. Measurements taken by such devices would include errors caused by fringes on interference patterns they produced. Therefore, what is also needed is an approach that permits interferometric displacement measurements over a wide range of displacements with consistent accuracy.
Heretofore, the requirements of removing further degrees of uncertainty from multi-color photons, producing an Nth-order interference pattern (where Nxe2x89xa74) with fewer than four emergent beams and performing interferometric displacement measurements over a wide range of displacement with consistent accuracy have not been fully met. What is needed is a solution that addresses these requirements.
There is a need for the following embodiments. Of course, the invention is not limited to these embodiments.
According to an aspect of the invention, a method comprises: downconverting a beam of coherent energy to provide a beam of multi-color entangled photons; converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; changing a phase of at least a portion of the converged multi-color entangled photon beam to generate a first interferometeric multi-color entangled photon beam; and combining the first interferometric multi-color entangled photon beam with a second interferometric multi-color entangled photon beam within a single beamsplitter. According to another aspect of the invention, an apparatus comprises: a multi-refringent device optically coupled to a source of coherent energy, the multi-refringent device providing a beam of multi-color entangled photons; a condenser device optically coupled to the multi-refringent device, the condenser device converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; a tunable phase adjuster optically coupled to the condenser device, the tunable phase adjuster changing a phase of at least a portion of the converged multi-color entangled photon beam to generate a first interferometeric multi-color entangled photon beam; and a beam splitter optically coupled to the condenser device, the beam splitter combining the first interferometeric multi-color entangled photon beam with a second interferometric multi-color entangled photon beam.
According to another aspect of the invention, a method comprises: downconverting a beam of coherent energy to provide a beam of multi-color entangled photons; converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; transforming at least a portion of the converged multi-color entangled photon beam by interaction with a sample to generate an entangle photon specimen beam; and combining the entangled photon specimen beam with an entangled photon reference beam within a single beamsplitter. According to another aspect of the invention, an apparatus comprises: a multi-refringent device providing a beam of multi-color entangled photons; a condenser device optically coupled to the multi-refringent device, the condenser device converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; a beam probe director and specimen assembly optically coupled to the condenser device; and a beam splitter optically coupled to the beam probe director and specimen assembly, the beam splitter combining an entangled photon specimen beam from the beam probe director and specimen assembly with an entangled photon reference beam. These, and other, embodiments of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating various embodiments of the invention and numerous specific details thereof, is given by way of illustration and not of limitation. Many substitutions, modifications, additions and/or rearrangements may be made within the scope of the invention without departing from the spirit thereof, and the invention includes all such substitutions, modifications, additions and/or rearrangements.